The invention relates to a plug-in pump for an internal combustion engine.
A plug-in pump of this kind is known from EP 0 543 301 A1 (especially FIG. 2) whose pump part and actuating part plug into a receiving bore in the cylinder block of an internal combustion engine. The pump part that has a pump piston in the pump housing is structurally separate from the actuating part with the roller tappet that is driven by the cam, but the pump and actuating part have an operating connection with one another. The lengthwise axis of the plug-in pump runs transversely to the axis of the camshaft and intersects the camshaft axis at its imaginary extension.
This camshaft also has cams that actuate the charge-changing valves of the internal combustion engine by push rods adjacent to the respective receiving bores of the plug-in pump of each cylinder.
The goal of the invention is to recover space in the cylinder block in its lengthwise extent by special positioning of the cam-driven plug-in pumps, while simultaneously improving the running behavior and/or the alignment of the rollers of the roller tappets that are guided in a lengthwise displaceable manner and, simultaneously with this special positioning, also to simplify installation and removal of the plug-in pumps in order to minimize the cost of repair resulting from normal wear.
These and other goals have been achieved according to the present invention by providing a plug-in pump for an internal combustion engine with a receiving bore provided in the cylinder block for the plug-in pump, said pump comprising a pump part with a pump piston guided in a pump housing and an actuating part with a cam-driven and spring-loaded roller tappet, and with a lengthwise axis of said pump extending transversely to a camshaft axis, piston guides for intake and exhaust valves of each cylinder being adjacent to the receiving bore of the plug-in pump, wherein an imaginary extension of the lengthwise axis of the plug-in pump at a distance from the camshaft axis such that the imaginary extension of the lengthwise axis of the plug-in pump intersects a plane that runs perpendicularly through the camshaft axis below the camshaft axis, the pump part and the actuating part being combined into a unit by a sleeve that fits around both parts and is inserted into the receiving bore, with the roller tappet being guided in the sleeve in a lengthwise displaceable manner.
By virtue of the positioning of the plug-in pumps according to the invention, whose lengthwise axes are located on their imaginary extensions at a specific distance from the camshaft axis and intersect a plane that runs perpendicularly through the axis of the camshaft below the camshaft axis, a greater distance from the cylinder axis and a closer spacing of the pushrod guides of the intake and exhaust valves is achieved so that the amount of space occupied lengthwise by the cylinder block can be reduced since the spacing of the cylinders arranged in line can be reduced. At the same time that space is gained, weight is reduced.
The pump part and actuating part of the plug-in pump according to the invention are combined in terms of design in a module by a sleeve that surrounds both parts and plugs into the receiving bore so that the pump part and actuating part can be removed in simple fashion from the cylinder block or can be plugged into the cylinder block as a one-piece element. Thus, the parts that are subject to wear are located in the plug-in pump and not in the cylinder block. No finishing work is required in the cylinder block when there are signs of wear. The unit is designed so it can be tested.
The special guidance of the roller tappet in the sleeve produces a form of protection against twisting that is not subject to difficulties.
By virtue of the special arrangement of the plug-in pump relative to the camshaft on the one hand and the special mounting of the roller tappet in the sleeve on the other, an alignment of the roller with the roller tappet is achieved that permits a much improved and/or more stable running behavior.
Although a cam-tappet system with a roller tappet for an injection pump is known from DE 40 40 937 A1, in which the roller axis is offset, this offset arrangement serves exclusively to prevent twisting.
A plug-in pump is known from DE 42 27 853A1 in which a thin-walled sliding sleeve is located between the roller tappet of the cam drive that can move back and forth in a bore in the block of the internal combustion engine. The rotational position of the roller tappet is secured by a pin and groove connection.
An advantageous improvement on the invention is obtained by the special arrangement of the fuel supply and the special design of the fuel connection in the critical area of two adjoining block parts.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.